Given the associated mammal fauna and the geological context, the find layer has been placed in the early Middle Pleistocene, but confirmatory chronometric evidence has hitherto been missing.
This result demonstrates that the mandible is the oldest hominin fossil reported to date from central and northern Europe and raises questions concerning the phyletic relationship of ” fossils from Trinil in Java, the Mauer jaw is one of the classic finds of paleoanthropology.
It was found on October 21, 1907, at a depth of 24 m in the Grafenrain sand pit, resting in fluvial sediments named the “Mauer sands” (1).
Magnetostratigraphic studies on clay layers below and within the Mauer sands show normal polarity.
Thus, they belong to the Brunhes chron and are younger than 780,000 y (3).
The age of terrestrial Quaternary deposits beyond 400 ka is difficult to assess by chronometric dating, particularly when volcanic layers are missing.
Earlier attempts to date the Mauer sands, namely by thermoluminescence of feldspar and electron spin resonance (ESR) of quartz as well as uranium-series (US) dating of an elephant tusk, were unsatisfactory (3).
Age estimates for the Mauer mandible have been advanced previously.
The Mauer sands are overlain by several Middle and Late Pleistocene glacial loess layers with interstratified interglacial paleosoil horizons, which constrain the age of the fossil to older than 350 ka (3).
The IR-RF technique dates the last light-exposure of sediment grains (i.e., their depositional age).
Ten samples from six sediment layers were analyzed using a single-aliquot protocol, which yields a series of ages on small subsamples (1 to 2 mg) of potassium feldspar grains ().
In the meantime, chronometric technologies have advanced, particularly in their range applicability.